My car doesn’t get anything like those MPG figures , it averages 33mpg or just over 8 L/100km but I think that is pretty good for a 3 litre turbo diesel, my little 1.5 litre petrol Colt only managed about 44mpg.
I have a spreadsheet (of course) but basically you fill the tank and note the Odo reading then drive until it is time to fill again. Then you fill it up, note the amount of fuel you put in and the Odo reading.
An odometer, shows the km/miles the car has travelled on your dash, every car has one, Arthur Daley used to wind them back. You don’t need a spreadsheet just a piece of paper and a pencil.
You subtract the first odo reading from the second one giving you the distance you have travelled on the the fuel you had to add. Divide the distance by the amount of fuel used which will give you miles per litre then divide by 4.546 to get MPG. You are allowed to use a calculator and it would be more accurate the more times you do it.
With this sort of travel I would have thought it would be cheaper to use a taxi/Uber; when you consider rego, insurance, fuel, depreciation etc, owning a car makes no sense.
I’ve just reminded myself about why I sold my Skoda diesel several years ago (in part ex. for a new car). Since we both stopped working, I realised that diesels need to be driven regularly for a specific distance in order to avoid undue wear or damage to the engine. As we do much less driving now (on a regular basis) we decided it best to go for a petrol engine.
I might look up the details again before we replace this car (which has some annoying things we don’t like) and, as we’ll be buying a different type, it might still be worth considering a diesel…
even if we have to keep adding AdBlue!